Electrochemical Instrumentation

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CH Instruments

1 Overview

CH Instruments was established in 1994. Our first instrument series, the Model 600 series electrochemical analyzer/workstation, was introduced at the end of 1994. Since then, new products have been added to provide a full line of electrochemical instrumentation: Model 400A Series Time-Resolved Electrochemical Quartz Crystal Microbalance (EQCM): for electro-deposition, adsorption, and chemical and biological sensor studies. Model 600D Series Potentiostat/Galvanostat: for general purpose electrochemical measurements, such as kinetic measurements, electroanalysis, fundamental research, corrosion, and battery studies. Model 700D Series Bipotentiostat: for rotating ring-disk electrodes (RRDE) and other cases where dual channel measurements are essential. Model 800C Series Electrochemical Detector: for either single or dual channel electrochemical detection of flow cell, capillary electrophoresis and liquid chromatography, for chemical and biological sensors, and conventional electroanalysis. Model 920C Scanning Electrochemical Microscope (SECM): for electrode surface, corrosion, biological samples, solid dissolution, liquid/liquid interfaces and membranes studies. Model 1000A Series Multi-potentiostat: 8-channel potentiostat for array electrode characterization and sensor studies. It can be used for eight independent cells or for eight working electrodes in a same solution. Model 1100A Power Potentiostat/Galvanostat: for applications involving higher current and compliance voltage. Model 1200A Handheld Potentiostat/Bipotentiostat: for electroanalysis, sensor studies, and field applications. Model 1550A Pico Liter Solution Dispenser: for making high density and high accuracy solution arrays. All models are controlled by an external PC under the Windows 95/98/NT/Me/2000/XP environment. The instruments are easy to install and use. No plug-in card or other hardware is required on the PC side. These instruments provide a rich repertoire of electrochemical techniques. Most well-established electrochemical techniques can be readily employed, including potential sweep, step, pulse, alternating current, stripping, and various other techniques. For each instrument series, we provide various models to suit different needs and budgets. Our instruments offer superior performance at competitive prices, and are ideal for both research and teaching purposes.

Model 400A Time-Resolved Electrochemical Quartz Crystal Microbalance

The quartz crystal microbalance (QCM) is a variant of acoustic wave microsensors that are capable of ultrasensitive mass measurements. Under favorable conditions, a typical QCM can measure a mass change of 0.1-1 ng/cm2. QCM oscillates in a mechanically resonant shear mode under the influence of a high frequency AC electric field which is applied across the thickness of the crystal. Figure 1b shows an edge view of a QCM crystal that is undergoing the shear distortion from the oscillation. The central portions of the top and bottom sides of the crystal are coated with a typically disk-shaped thin film of gold or other metals. The mass sensitivity of the QCM originates from the relationship between the oscillation frequency on the total mass of the crystal and the adlayers of materials residing at the metal-coated crystals, given by the Sauerbrey equation below:

2 ∆f = -2f0 ∆m / [A sqrt(µρ)] where f0 is the resonant frequency of the fundamental mode of the crystal, A is the area of the gold disk coated onto the crystal, ρ is the density of the crystal (= 2.684 g/cm3), and µ is the shear modulus of quartz (= 2.947 x 1011 g/cm.s2). Using a crystal with a 7.995-MHz fundamental frequency (as used in our measurements) as an example, a net change of 1 Hz corresponds to 1.34 ng of materials adsorbed or desorbed onto the crystal surface of an area of 0.196 cm2. QCM and the combination of QCM with electrochemistry (EQCM) have been widely employed for the determination of metals deposited onto the crystal, studies of ion-transport processes in polymer films, biosensor development, and investigations of the kinetics of adsorption/desorption of adsorbate molecules. In EQCM experiments, the measurements of the various electrochemical parameters, such as potential, current and charge at the working electrode, and the acquisition of the corresponding frequency change, can be conducted simultaneously with the experimental setup shown in Figure 1a. For any model in the CHI400A series, the application of a specific potential waveform (e.g., triangular potential waveform for cyclic voltammetric experiments), as well as subsequent current measurements and the frequency counting, was carried out with a potentiostat/frequency counter, in turn controlled by a computer.

Figure 1. Schematic representation of a typical EQCM instrument. (a) The quartz crystal has a fundamental frequency of 7.995 MHz and is coated with thin gold films on both sides. The gold disk deposited on the top side of the crystal is in contact with the electrolyte solution and used as the working electrode. The top view of the gold- coated crystal is also shown. (b) Edge view of QCM crystal showing shear deformation. The disk thickness and shear deformation have been exaggerated for clarity.

The CHI400A series contains a quartz crystal oscillator, frequency counter, fast digital function generator, high-resolution and high-speed data acquisition circuitry, potentiostat, and a galvanostat (Model 440A only). The

3 QCM is integrated with potentiostat and galvanostat, making the EQCM study simple and convenient. Instead of measuring the frequency directly, the CHI400A series uses time-resolved mode. The frequency signal of the QCM is subtracted from a standard reference frequency. The difference is then measured by a reciprocal technique, which greatly reduces the time needed to sample the QCM signal and gives much better time resolution of the QCM signal. With the direct counting method, a 1 Hz QCM resolution requires 1 second of sampling time, and a 0.1 Hz resolution requires 10 seconds of sampling time. The time-resolved mode allows the QCM signal to be measured in milliseconds with much better resolution. The potential control range of the instrument is ±10 V and the current range is ±250 mA. Besides QCM and EQCM measurements, the instrument can also be used for general-purpose electrochemical applications, which are integrated. The instrument is very sensitive and very fast, capable of measuring current down to the picoampere level. The scan rate in cyclic voltammetry can be up to 100 V/s with a 0.1 mV potential increment or 2000 V/s with a 2 mV potential increment. Figure 2 shows the voltammogram of underpotential and bulk depositions of Pb from a 0.1 M HClO4 solution containing 1 mM Pb2+, and the corresponding frequency changes have been plotted as a function of the applied potential. In Figure 2a, the cathodic peaks at –0.28 V and at ca. –0.59 V have been assigned to the underpotential deposition of monolayer Pb and the bulk deposition of multlayers of Pb, respectively, whereas the anodic peaks at –0.41 V and at –0.28 V are attributable to the stripping of the deposited Pb. The frequency-potential diagram (Figure 2b) displays the frequency decrease due to the deposition of monolayer Pb (about 25 Hz or 33.5 ng between –0.28 V and –0.59 V) and the more drastic frequency decrease arising from bulk Pb deposition (a net change of 425 Hz or 573.8 ng at ca. –0.5 V).

Figure 2. Voltammogram and QCM data of Pb underpotential deposition. Scan rate = 0.05 V/s.

4 Figure 3 depicts the voltammogram of the oxidation of pyrrole to form polypyrrole film at the gold-coated crystal and the corresponding frequency change. Five scan segments between the lower limit of –1.0 V and the upper limit of 1.0 V were conducted in this experiment. As clearly shown in Figure 3a, pyrrole monomer can be oxidized to its radical at ca. 0.65 V. When this occurred, a thin polypyrrole film was formed, resulting in a decrease of the fundamental frequency of the quartz crystal (Figure 3b). During the first potential cycle, the net frequency change was found to be 1150 Hz. The frequency ceased to change, as the potential became insufficiently positive for the synthesis of polypyrrole film. The subsequent potential cycles displayed in Figure 3 demonstrate the continuous growth of polypyrrole film and the further frequency decrease or mass increase at the crystal. A fast scan rate (0.1 V/s) was employed.

Figure 3. Voltammogram and QCM data of oxidation of pyrrole to form polypyrrole film. Scan rate 0.1 V/s.

The instrument can also be used for regular QCM. Figure 4 shows the QCM data of flow cell detection. The total frequency change is less than 8 Hz. The long term drift and noise levels are extremely low. The model 400A series is our upgrade to the model 400 series. The redesigned instrument contains a new processor (about 50 times faster than the 400) and FLASH memory (allowing instrument updates to be distributed by e-mail instead of the shipment of an EPROM chip).

Figure 4. A typical flow injection-QCM experiment. As soon as the sample is injected, the QCM starts recording the frequency change (t = 0). The pump is stopped at 460 s (where a small glitch on the curve can be seen). The reaction is completed about 40 min after sample injection. The total monitoring time is over 1 hr. A net change of 8 Hz is monitored. After 40 min or so, the frequency becomes very stable again (for at least more than 20 min, the frequency drift is much less than 1 Hz).

The 400A series has a serial port (default) and a USB for data communication with the PC. You can select either serial port or USB (but not both) by changing the jumper setting on the board. A 16-bit highly stable bias circuitry is added for current or potential bias. This allows wider dynamic range is ac measurements. It can also be used to re-zero the dc current output. The EQCM cell consists of three round Teflon pieces (Figure 1a). The total height is 37 mm with a diameter of 35 mm. The top piece is the cell top to hold reference and counter electrodes. There are also two 2 mm holes for manual purging. The center piece is the solution cell, and the bottom piece is for mounting purposes. Four screws are used to tighten the O-ring seal between the bottom center piece. The quartz crystal is located between the center and bottom pieces. The diameter of the quartz crystal is 13.7 mm. The gold electrode diameter is 5.1 mm.

6 Specifications

Potentiostat CV and LSV scan rate: 0.000001 to 2000 V/s Galvanostat (Model 440A) Potential increment during scan: 0.1 mV @ 100 V/s Potential range: -10 to 10V CA and CC pulse width: 0.0001 to 1000 sec Potentiostat rise time: < 2 us CA and CC Steps: 320 Compliance voltage: ±12 V DPV and NPV pulse width: 0.0001 to 10 sec 3- or 4-electrode configuration SWV frequency: 1 to 100 kHz Current range: 250 mA ACV frequency: 1 to 10 kHz Reference electrode input impedance: 1×1012 ohm SHACV frequency: 1 to 5 kHz Sensitivity scale: 1×10-12 - 0.1 A/V in 34 ranges Automatic potential and current zeroing Input bias current: < 50 pA Low-pass signal filters, automatic and manual setting Current measurement resolution: < 0.01 pA RDE rotation control output: 0 - 10 V (430 and up) Minimum potential increment in CV: 100 µV Cell control: purge, stir, knock Data acquisition: 16 bit @ 200 kHz Data length: 128K – 4096K selectable Frequency resolution: < 0.1 Hz Dimension: 12.5”(W) × 11”(D) × 4.75”(H) QCM maximum sampling rate: 1 kHz Oscillator Box (external): Automatic and manual iR compensation 4.75"(L) × 2.6" (W) × 1.55" (H) Weight: 15 Lb.

Differences of 400A Series Models

Functions 400A 410A 420A 430A 440A Cyclic Voltammetry (CV) z z z z z Linear Sweep Voltammetry (LSV) & z z z z z Staircase Voltammetry (SCV) #,& z z Tafel Plot (TAFEL) z z Chronoamperometry (CA) z z z z Chronocoulometry (CC) z z z z Differential Pulse Voltammetry (DPV) #,& z z z z Normal Pulse Voltammetry (NPV) #,& z z z z Differential Normal Pulse Voltammetry (DPNV)#,& z Square Wave Voltammetry (SWV) & z z z AC Voltammetry (ACV) #,&,$ z z 2nd Harmonic AC Voltammetry (SHACV) #,&,$ z z Amperometric I-t Curve (I-t) z z Differential Pulse Amperometry (DPA) z Double Differential Pulse Amperometry (DDPA) z Triple Pulse Amperometry (TPA) z Bulk Electrolysis with Coulometry (BE) z z z z Hydrodynamic Modulation Voltammetry (HMV) z Sweep-Step Functions (SSF) z Multi-Potential Steps (STEP) z Chronopotentiometry (CP) z Chronopotentiometry with Current Ramp (CPCR) z Potentiometric Stripping Analysis (PSA) z Open Circuit Potential - Time (OCPT) z z z z z Quartz Crystal Microbalance (QCM) z z z z z

Galvanostat z RDE control (0-10V output) z z Full version of CV simulator z z Limited version of CV simulator z z z iR Compensation z z z z z

#: Corresponding polarographic mode can be performed. &: Corresponding stripping mode can be performed. $: Phase selective data are available.

7 Model 600D Series Electrochemical Analyzer / Workstation

The Model 600D series is designed for general purpose electrochemical measurements. The figure below shows the block diagram of the instrument. The system contains a fast digital function generator, high speed data acquisition circuitry, potentiostat, and a galvanostat (available only in select models). The potential control range is ±10 V and the current range is ±250 mA. The instrument is capable of measuring current down to tens of picoamperes. The steady state current of a 10 µm disk electrode can be readily measured without external adapters. With the CHI200B Picoamp Booster and Faraday Cage (fully automatic and compatible with the CHI600D series), currents down to 1 pA can be measured. These instruments are very fast. The function generator can update at a 10 MHz rate, and the maximum sampling rate is 1 MHz at 16-bit resolution. The instrument provides very wide dynamic range on experimental time scales. For instance, the scan rate in cyclic voltammetry can be up to 1000 V/s with a 0.1 mV potential increment or 5000 V/s with a 1 mV potential increment. The potentiostat/galvanostat uses a 4-electrode configuration, allowing it to be used for liquid/liquid interface measurements and eliminating the effect of contacting resistance of connectors and relays for high current measurements. Multiple data acquisition systems allow an external input signal (such as spectroscopy signals to be recorded simultaneously with electrochemical data). The instrument will also automatically re-zero both potential and current, so that periodic re-calibration of the instrument can be avoided.

The 600D series is the upgrade to our very popular 600/600A/600B/600C series. The instrument utilizes FLASH memory, allowing instrument updates to be distributed by e-mail instead of the shipment of an EPROM chip. The 600D series has a serial port (default) and a USB for data communication with the PC. You can select either serial port or USB (but not both) by changing the jumper setting on the board. The 600D series also includes a true integrator for chronocoulometry. A 16-bit highly stable bias circuitry is used for current or potential bias. This allows wider dynamic range in ac measurements. It can also be used for re-zero the dc current output. The model 600D series can be upgraded to a bipotentiostat. The model 700D series will be an add-on board to the 600D series. It will therefore be identical to the 600D series when used for single channel measurements. When it is used as a bipotentiostat, the second channel can be controlled at an independent constant potential to scan or step at the same potential as the first channel, or to scan with a constant potential difference with the first channel. The second channel is available for many voltammetric and amperometric techniques.

8 The instrument also provides various electrochemical techniques, Windows-based software, and integrated digital CV simulator, impedance simulation and fitting program. These features provide powerful tools for both electrochemical mechanistic studies and trace analysis. We provide several different models in the 600D series. The following table compares the different models. Other than what is listed, the specifications and features of these models are identical. Models 600D and 610D are basic units for mechanistic study and electrochemical analysis, respectively. They are also great for teaching purposes. Models 602D and 604D are for corrosion studies. Models 620D and 630D are comprehensive electrochemical analyzers. Models 650D and 660D are advanced electrochemical workstations.

Specifications

Potentiostat CV and LSV scan rate: 0.000001 to 5000 V/s Galvanostat (Model 660D) Potential increment during scan: 0.1 mV @ 1000 V/s Potential range: -10 to 10 V CA and CC pulse width: 0.0001 to 1000 sec Potentiostat rise time: < 1 us CA and CC Steps: 320 Compliance voltage: ±12 V True integrator for CC 3- or 4-electrode configuration DPV and NPV pulse width: 0.001 to 10 sec Current range: 250 mA SWV frequency: 1 to 100 kHz Reference electrode input impedance: 1×1012 ohm ACV frequency: 0.1 to 10 kHz Sensitivity scale: 1×10-12 - 0.1 A/V in 12 ranges SHACV frequency: 0.1 to 5 kHz Input bias current: < 50 pA IMP frequency: 0.00001 to 100 kHz Current measurement resolution: < 0.01 pA Automatic potential and current zeroing Minimum potential increment in CV: 100 µV Potential, current low-pass filters, covering 8-decade Potential update rate: 10 MHz frequency range, Automatic and manual setting Fast data acquisition: 16 bit @ 1 MHz RDE rotation control voltage output: 0 - 10 V (Model 630D External signal recording channel and up) Automatic and manual iR compensation Cell control: purge, stir, knock Flash memory for quick software update Maximum data length: 128K-8192K selectable Serial port or USB selectable for data communication Dimension: 12.5”(W) × 11”(D) × 4.75”(H) Weight: 15 Lb.

Square wave voltammogram. Amperometric i-t Curve.

9 Differences of 600D Series Models

Functions 600D 602D 604D 610D 620D 630D 650D 660D Cyclic Voltammetry (CV) z z z z z z z z Linear Sweep Voltammetry (LSV) & z z z z z z z z Staircase Voltammetry (SCV) #,& z z z Tafel Plot (TAFEL) z z z z z Chronoamperometry (CA) z z z z z z z Chronocoulometry (CC) z z z z z z z Differential Pulse Voltammetry (DPV) #,& z z z z z Normal Pulse Voltammetry (NPV) #,& z z z z z Differential Normal Pulse Voltammetry (DPNV)#,& z Square Wave Voltammetry (SWV) & z z z z AC Voltammetry (ACV) #,&,$ z z z 2nd Harmonic AC Voltammetry (SHACV) #,&,$ z z z Amperometric i-t Curve (i-t) z z z Differential Pulse Amperometry (DPA) z Double Differential Pulse Amperometry (DDPA) z Triple Pulse Amperometry (TPA) z Integrated Pulse Amperometric Detection (IPAD) z Bulk Electrolysis with Coulometry (BE) z z z z z z z Hydrodynamic Modulation Voltammetry (HMV) z z Sweep-Step Functions (SSF) z z Multi-Potential Steps (STEP) z z AC Impedance (IMP) z z z Impedance - Time (IMPT) z z z Impedance - Potential (IMPE) z z z Chronopotentiometry (CP) z Chronopotentiometry with Current Ramp (CPCR) z Multi-Current Steps (ISTEP) z Potentiometric Stripping Analysis (PSA) z Electrochemical Noise Measurement (ECN) z Open Circuit Potential - Time (OCPT) z z z z z z z z

Galvanostat z RDE control (0-10V output) z z z Full version of CV simulator z z z Limited version of CV simulator z z z z z Impedance Simulation and fitting z z z iR Compensation z z z z z z z z External Potential Input z z z z z z z z Auxiliary Signal Measurement Channel z z z z z z z z

#: Corresponding polarographic mode can be performed. &: Corresponding stripping mode can be performed. $: Phase selective data are available.

Cyclic voltammogram at 1000V/s. Phase selective second harmonic AC voltammogram.

10 Model 700D Series Bipotentiostat

The Model 700D series are computerized general purpose potentiostat / bipotentiostat / galvanostat instruments. A typical application involves a rotating ring-disk electrode (RRDE), but these systems can also be used for other applications where dual channel measurements are essential, such as dual channel electrochemical detection. The system contains a fast digital function generator, high speed data acquisition circuitry, (bi)potentiostat, and a galvanostat (only available in select models). The potential control range is ±10 V and the current range is ±250 mA. The instrument is capable of measuring current down to tens of picoamperes. The steady state current of a 10 µm disk electrode can be readily measured without external adapters. With the CHI200B Picoamp Booster and Faraday Cage (fully automatic and compatible with the CHI700D series), currents down to 1 pA can be measured (primary current channel only). These instruments are very fast. The function generator can update at a 10 MHz rate, and the maximum sampling rate is 1 MHz at 16-bit resolution. The instrument provides a very wide dynamic range on experimental time scales. For instance, the scan rate in cyclic voltammetry can be up to 1000 V/s with a 0.1 mV potential increment or 5000 V/s with a 1 mV potential increment. The potentiostat / galvanostat uses a 4-electrode configuration, allowing it to be used for liquid/liquid interface measurements and eliminating the effect of contacting resistance of connectors and relays for high current measurements. Multiple data acquisition systems allow an external input signal (such as spectroscopy signals to be recorded simultaneously with electrochemical data). The instrument will also automatically re-zero both potential and current, so that periodic re-calibration of the instrument can be avoided. The 700D series shares many common features with the 600D series. When used as a single channel potentiostat, the instrument is identical to the model 600D series. The bipotentiostat is realized by adding the second channel potential control and current measurement board to the model 600D series. There are also two filter stages, three extra gain stages, and a channel selection circuitry on the board. When it is used as a bipotentiostat, the second channel can be controlled at an independent constant potential, to scan or step at the same potential as the first channel. In case of CV, it can also scan with a constant potential difference with the first channel. Techniques available for the second channel include CV, LSV, SCV, CA, DPV, NPV, SWV, and i-t. The 700D series is the upgrade to our very popular 700/700A/700B/700C series. The instrument utilizes FLASH memory, allowing instrument updates to be distributed by e-mail instead of the shipment of an EPROM chip. The 700D series has a serial port (default) and a USB for data communication with the PC. You can select either serial port or USB (but not both) by changing the jumper setting on the board. The 700D series also has a true integrator for chronocoulometry. A 16-bit highly stable bias circuitry is used for current or potential bias. This allows wider dynamic range is ac measurements. It can also be used for re-zero the dc current output. When used as a single channel potentiostat, the instrument is identical to the model 600D series. The bipotentiostat is realized by adding the 2nd channel potential control and current measurement board. When it is used as bipotentiostat, the 2nd channel can be controlled at a independent constant potential, to scan or step at the same potential as the first channel, and to scan with a constant potential difference with the first channel. The instrument also provides various electrochemical techniques, Windows-based software, and integrated digital CV simulator, impedance simulation and fitting program. These features provide powerful tools for both electrochemical mechanistic studies and trace analysis. We provide several different models in the 700D series. The following table compares the different models. Other than what is listed, the specifications and features of these models are identical. Models 700D and 710D are basic units for mechanistic study and electrochemical analysis, respectively. Models 720D and 730D are comprehensive electrochemical analyzers. Model 750D and 760D are advanced electrochemical workstations.

11 Specifications

Potentiostat CV and LSV scan rate: 0.000001 to 5000 V/s Bipotentiostat Potential increment during scan: 0.1 mV @ 1000 V/s Galvanostat CA and CC pulse width: 0.0001 to 1000 sec Potentiostat rise time: < 1 µs CA and CC Steps: 320 Potential range: ±10 V for both channels True integrator for CC Compliance voltage: ±12 V DPV and NPV pulse width: 0.001 to 10 sec Current: 0.25 A if single channel, or 0.25 A total for two SWV frequency: 1 to 100 kHz ACV frequency: 0.1 to 10 kHz channels 12 SHACV frequency: 0.1 to 5 kHz Input impedance of reference electrode: 10 ohm IMP frequency: 0.00001 to 100 kHz -12 Sensitivity scale: 1×10 - 0.1 A/V in 12 ranges Automatic potential and current zeroing Input bias current: < 50 pA Potential, current low-pass filters, covering 8-decade Current measurement resolution: < 0.01 pA frequency range, Automatic and manual setting Minimum potential increment in CV: 100 µV RDE rotation control voltage output: 0 - 10 V Potential update rate: 10 MHz Cell control: purge, stir, knock Fast data acquisition: 16 bit @ 1 MHz Flash memory for quick software update External voltage signal recording channel Serial port or USB selectable for data communication External potential input Maximum data length: 128K-4096K selectable Automatic and manual iR compensation Dimension: 12.5”(W) × 11”(D) × 4.75”(H) Weight: 15 Lb.

Chronoamperometric data. Voltammogram at rotating ring-disk electrode.

12 Differences of 700D Series Models

Functions 700D 710D 720D 730D 750D 760D Cyclic Voltammetry (CV)* z z z z z z Linear Sweep Voltammetry (LSV) &,* z z z z z z Staircase Voltammetry (SCV) #,&,* z z z Tafel Plot (TAFEL) z z z Chronoamperometry (CA)* z z z z z Chronocoulometry (CC) z z z z z Differential Pulse Voltammetry (DPV) #,&,* z z z z z Normal Pulse Voltammetry (NPV) #,&,* z z z z z Differential Normal Pulse Voltammetry (DPNV)#,& z Square Wave Voltammetry (SWV) &,* z z z z AC Voltammetry (ACV) #,&,$ z z z 2nd Harmonic AC Voltammetry (SHACV) #,&,$ z z z Amperometric i-t Curve (i-t)* z z z Differential Pulse Amperometry (DPA) z Double Differential Pulse Amperometry (DDPA) z Triple Pulse Amperometry (TPA) z Integrated Pulse Amperometric Detection (IPAD) z Bulk Electrolysis with Coulometry (BE) z z z z z Hydrodynamic Modulation Voltammetry (HMV) z z Sweep-Step Functions (SSF) z z Multi-Potential Steps (STEP) z z AC Impedance (IMP) z z Impedance - Time (IMPT) z z Impedance - Potential (IMPE) z z Chronopotentiometry (CP) z Chronopotentiometry with Current Ramp (CPCR) z Multi-Current Steps (ISTEP) z Potentiometric Stripping Analysis (PSA) z Electrochemical Noise Measurement (ECN) z Open Circuit Potential - Time (OCPT) z z z z z z

Galvanostat z RDE control (0-10V output) z z z Full version of CV simulator z z z Limited version of CV simulator z z z Impedance Simulation and Fitting z z iR Compensation z z z z z z External Potential Input z z z z z z Auxiliary Signal Measurement Channel z z z z z z

#: Corresponding polarographic mode can be performed. &: Corresponding stripping mode can be performed. $: Phase selective data are available. *: Second channel (bipotentiostat mode) can be performed.

13 Model 800C Series Electrochemical Detector

The Model 800C series is designed for electrochemical detection. This instrument can be used for monitoring the current passing through a flow cell in liquid chromatography/electrochemistry and in-flow injection analysis, as well as other electroanalytical applications. Each instrument contains a digital function generator, a data acquisition system, and a potentiostat / bipotentiostat / Galvanostat. The potential control range is ±10 V and the current range is ±10 mA. These instruments are capable of measuring currents down to picoamperes. This series is designed for analytical purposes that require high sensitivity and low noise levels. It has a maximum sampling rate of 1M Hz at 16-bit. The circuitry has very low electrical noise. The instrument allows an external input signal (such as spectroscopy signals) to be recorded simultaneously with electrochemical data. When it is used for amperometric detection, three decades of current scales are plotted during the experiment to display signals of various magnitudes clearly. This model has superior ease of use compared with analog instruments, as well as data storage and analysis capabilities, without the need for recorder/baseline adjustments. It also provides a much larger current dynamic range, so that separate runs for large and weak signals can be avoided. The Model 8×0C is for single channel measurements, and the Model 8×2C contains a bipotentiostat and is for dual channel measurements. As a bipotentiostat, it is well suited to rotating ring-disk electrodes applications. It can also be used for other applications where dual channel measurements are essential. Dual channel measurements are available for CV, LSV, CA, DPV, NPV, SWV, and amperometric i-t curves. The 2nd channel can be controlled at a independent constant potential, to scan or step at the same potential as the first channel, and to CV scan with a constant potential difference with the first channel. The model 800C series is our upgrade to the model 800/800A/800B series. The instrument utilizes FLASH memory, allowing instrument updates to be distributed by e-mail instead of the shipment of an EPROM chip. The 800C series has a serial port (default) and a USB for data communication with the PC. You can select either serial port or USB (but not both) by changing the jumper setting on the board. The 800C series also has a true integrator for chronocoulometry. We provide several different models in the 800C series. The following table compares the different models. Other than what is listed, the specifications and features of these models are identical. Models 800C/802C and 810C/812C are mainly for flow cell detection. Models 820C/822C cannot be used for flow cell detection, but are intended for voltammetry applications. Models 830C/832C are comprehensive electrochemical analyzers that can be used for electrochemical detection, voltammetry, and other applications. Models 840C/842C and 850C/852C are more advanced models with a galvanostat.

Real time data display for flow cell detection.

14 Specifications

Potentiostat CC and CA pulse width: 0.0001 to 1000 sec Bipotentiostat True integrator for CC Galvanostat (840C/842C/850C/852C) DPV and NPV pulse width: 0.001 to 10 sec Potential range: ±10 V SWV frequency: 1 to 100 kHz Compliance voltage: ±12 V ACV frequency: 0.1 to 10 kHz Current range: 0 to ±0.01 A SHACV frequency: 0.1 to 5 kHz 3- or 4-electrode configuration Dual channel measurements for CV, LSV, CA, DPV, NPV, SWV, i-t Input impedance of reference electrode: 1012 ohm Cell control: purge, stir, knock Sensitivity scale: 1×10-12 - 0.001 A/V in 10 ranges Automatic potential and current zeroing Input bias current: < 5 pA Current low-pass filters, covering 8-decade frequency Current measurement resolution: < 0.01 pA range, Automatic and manual setting Fast data acquisition: 16 bit @ 1M Hz RDE control output: 0-10V (corresponding to 0-10000rpm) External voltage signal recording channel Flash memory for quick software update External potential input Serial port or USB port selectable for data communication Automatic and manual iR compensation Maximum data length: 128K - 8192K selectable Potential and current analog output Dimension: 12.5”(W) × 11”(D) × 4.75”(H) CV and LSV scan rate: 1×10-6 to 500 V/s Weight: 15 Lb.

Differences of 800C Series Models

Functions 800C/802C 810C/812C 820C/822C 830C/832C 840C/842C 850C/852C Cyclic Voltammetry (CV)* z z z z z z Linear Sweep Voltammetry (LSV) &,* z z z z z z Staircase Voltammetry (SCV) #,&,* z Tafel Plot (TAFEL) z Chronoamperometry (CA)* z z z Chronocoulometry (CC) z z z Differential Pulse Voltammetry (DPV) #,&,* z z z z Normal Pulse Voltammetry (NPV) #,&,* z z z z Differential Normal Pulse Voltammetry (DPNV)#,& z Square Wave Voltammetry (SWV) &,* z z z z AC Voltammetry (ACV) #,&,$ z 2nd Harmonic AC Voltammetry (SHACV) #,&,$ z Amperometric i-t Curve (i-t)* z z z z z Differential Pulse Amperometry (DPA) z z z z Double Differential Pulse Amperometry (DDPA) z z z z Triple Pulse Amperometry (TPA) z z z z Integrated Pulse Amperometric Detection (IPAD) z Bulk Electrolysis with Coulometry (BE) z z z z Hydrodynamic Modulation Voltammetry (HMV) z Sweep-Step Functions (SSF) z z Multi-Potential Steps (STEP) z z Chronopotentiometry (CP) z z Chronopotentiometry with Current Ramp (CPCR) z z Multi-Current Steps (ISTEP) z z Potentiometric Stripping Analysis (PSA) z z z Electrochemical Noise Measurement (ECN) z Open Circuit Potential - Time z z z z z z

Galvanostat z z RDE control (0-10V output) z z Full version of CV simulator z z z Limited version of CV simulator z z z iR Compensation z z z z z z External Potential Input z z z z z z Auxiliary Signal Measurement Channel z z z z z z

15 #: Corresponding polarographic mode can be performed. &: Corresponding stripping mode can be performed. *: Second channel (bipotentiostat mode) can be performed.

16 Model 920C Scanning Electrochemical Microscope

The scanning electrochemical microscope (SECM) was introduced in 19891 as an instrument that could examine chemistry at high resolution near interfaces. By detecting reactions that occur at a small electrode (the tip) as it is scanned in close proximity to a surface, the SECM can be employed to obtain chemical reactivity images of surfaces and quantitative measurements of reaction rates. Numerous studies with the SECM have now been reported from a number of laboratories all over the world, and the instrument has been used for a wide range of applications, including studies of corrosion, biological systems (e.g., enzymes, skin, leaves), membranes, and liquid/liquid interfaces.2 Trapping and electrochemical detection of single molecules with the SECM has also been reported. The CHI920C Scanning Electrochemical Microscope consists of a digital function generator, a bipotentiostat, high resolution data acquisition circuitry, a three dimensional nanopositioner, and a sample and cell holder. Diagrams for the SECM and cell/sample holder are shown below. The three dimensional nanopositioner has a spatial resolution down to nanometers but it allows a maximum traveling distance of 50 millimeters. The potential control range of the bipotentiostat is ± 10 V and the current range is ± 250 mA. The instrument is capable of measuring current down to sub-picoamperes. In addition to SECM imaging, three other modes of operation are available for scanning probe applications: Surface Patterned Conditioning, Probe Scan Curve, and Probe Approach Curve. Surface Patterned Conditioning allows user to edit a pattern for surface conditioning by controlling the tip at two different potentials and durations. The Probe Scan Curve mode allows the probe to move in the X, Y, or Z direction while the probe and substrate potentials are controlled and currents are measured. The probe can be stopped when the current reaches a specified level. This is particularly useful in searching for an object on the surface and determining approach curves. The Probe Approach Curve mode allows the probe to approach the surface of the substrate. It is also very useful in distinguishing the surface process, using PID control. The step size is automatically adjusted to allow fast surface approach, without letting the probe touching the surface. The CHI920C is designed for scanning electrochemical microscopy, but many conventional electrochemical techniques are also integrated for convenience, such as CV, LSV, CA, CC, DPV, NPV, SWV, ACV, SHACV, i-t, DPA, DDPA, TPA, SSF, STEP, IMP, IMPE, IMPT, and CP. When it is used as a bipotentiostat, the second channel can be controlled at an independent constant potential, to scan or step at the same potential as the first channel, or to scan with a constant potential difference with the first channel. The second channel works with CV, LSV, CA, DPV, NPV, DNPV, SWV, and i-t. The CHI920C SECM is an upgrade from the CHI900B/CHI910B SECM. The stepper motor positioner now has a resolution of 4 nanometers with 50 mm travel distance. CHI920C will be the stepper motor positioner with a combination of closed loop 3-dimensional piezo positioner. The closed-loop piezo control allows improved linearity and reduced hysteresis of the piezo devices. The other improvements for the CHI920C over the CHI900B/910B include faster data acquisition (1M Hz 16-bit), higher current (250mA), faster CV (1000V/s at 0.1 mV potential increment), and ac impedance measurements.

1. A. J. Bard, F.-R. F. Fan, J. Kwak, and O. Lev, Anal. Chem. 61, 132 (1989); U.S. Patent No. 5,202,004 (April 13, 1993). 2. A. J. Bard, F.-R. Fan, M. V. Mirkin, in Electroanalytical Chemistry, A. J . Bard, Ed., Marcel Dekker, New York, 1994, Vol. 18, pp 243-373.

Diagram of Scanning Electrochemical Microscope

Cell/Sample Holder

Bipotentiostat (top) and Motor Controller Front View Bipotentiostat (top) and Motor Controller Rear View

18 CHI920C SECM Specifications Techniques

Nanopositioner: Scanning Probe Techniques X, Y, Z resolution: 1.6 nm with Piezo positioner, • SECM Imaging (SECM) : constant height, closed loop control constant current, 4 nm with stepper motor positioner potentiometric modes X, Y, Z total distance: 5 cm • Probe Approach Curves (PAC) Bipotentiostat: • Probe Scan Curve (PSC) : amperometric, Probe Potential: ± 10 V potentiometric and Substrate Potential: ± 10 V constant current modes Compliance Voltage: ± 12 V • Surface Patterned Conditioning (SPC) 3- or 4-electrode configuration Sweep Techniques Reference electrode input impedance: 1e12 ohm -12 -1 • Cyclic Voltammetry (CV) Current Sensitivity: 10 A/V to 10 A/V • Linear Sweep Voltammetry (LSV) Maximum Current: ± 250 mA • Tafel Plot (TAFEL) External signal recording channel Step and Pulse Techniques ADC Resolution: 16-bit @ 1 M Hz • Staircase Voltammetry (SCV) Galvanostat: Current range: ± 250 mA • Chronoamperometry (CA) Experimental Parameters: • Chronocoulometry (CC) CV and LSV scan rate: 0.000001 to 10,000 V/s • Differential Pulse Voltammetry (DPV) Potential increment during scan: 0.1 mV @1000 V/s • Normal Pulse Voltammetry (NPV) CC and CA pulse width: 0.0001 to 1000 sec • Differential Normal Pulse Voltammetry (DNPV) True integrator for CC • Square Wave Voltammetry (SWV) DPV and NPV pulse width: 0.001 to 10 sec AC Techniques SWV frequency: 1 to 100 kHz • AC Voltammetry (ACV) ACV frequency: 0.1 to 10 kHz • Second Harmonic AC Voltammetry (SHACV) SHACV frequency: 0.1 to 5 kHz • AC Impedance (IMP) IMP frequency: 0.00001 to 100 kHz • Impedance versus Potential (IMPE) Automatic potential and current zeroing • Impedance versus Time (IMPT) Automatic and manual iR compensation Galvanostatic Techniques Current low-pass filters, covering 8-decade • Chronopotentiometry (CP) frequency range, Automatic and manual setting • Chronopotentiometry with Current Ramp (CPCR) RDE control output: 0-10 V (corresponding to 0- • Multi-Current Steps (ISTEP) 10000 rpm) • Potentiometric Stripping Analysis (PSA) Flash memory for quick software update Serial port or USB port selectable for data Other Techniques communication • Amperometric i-t Curve (i-t) • Differential Pulse Amperometry (DPA) Other Features: • Double Differential Pulse Amperometry (DDPA) Real Time Absolute and Relative Distance Display Real Time Probe and Substrate Current Display • Triple Pulse Amperometry (TPA) Dual channel measurements for CV, LSV, CA, • Integrated Pulse Amperometric Detection (IPAD) DPV, NPV, SWV, i-t • Bulk Electrolysis with Coulometry (BE) Cell control: purge, stir, knock • Hydrodynamic Modulation Voltammetry (HMV) Automatic potential and current zeroing • Sweep-Step Functions (SSF) Current low-pass filters, covering 8-decade • Multi-Potential Steps (STEP) frequency range, Automatic and manual • Electrochemical Noise Measurements (ECN) setting • Open Circuit Potential - Time (OCPT) RDE control output: 0-10 V (corresponding to 0- • Various Stripping Voltammetry 10000 rpm) • Potentiometry Flash memory for quick software update Applications Serial port or USB port selectable for data • Electrode surface studies communication Digital CV simulator, user defined mechanisms • Corrosion Impedance simulator and fitting program • Biological samples • Solid dissolution • Liquid/liquid interfaces • Membranes

Principles and Applications of SECM

I. Operational Principles of SECM When the tip is rastered in the x-y plane above the

As in other types of scanning probe microscopes, substrate, the tip current variation represents changes in SECM is based on the movement of a very small topography or conductivity (or reactivity). One can electrode (the tip) near the surface of a conductive or separate topographic effects from conductivity effects insulating substrate.1 In amperometric SECM ex- by noting that over an insulator iT is always less than periments, the tip is usually a conventional ultra- iT,∞, while over a conductor iT is always greater than microelectrode (UME) fabricated as a conductive disk iT,∞. of metal or carbon in an insulating sheath of glass or In the feedback mode of the SECM operation as polymer. Potentiometric SECM experiments with ion- stated above, the overall redox process is essentially selective tips are also possible.2 confined to the thin layer between the tip and the In amperometric experiments, the tip current is substrate. In the substrate-generation/tip-collection perturbed by the presence of the substrate. When the tip (SG/TC) mode (when the substrate is a generator and is far (i.e. greater than several tip diameters) from the the tip is a collector), the tip travels within a thin 1b,3 substrate, as shown in Fig. 1A, the steady-state current, diffusion layer generated by the substrate electrode. There are some shortcomings which limit the iT,∞, is given by applicability of the SG/TC mode if the substrate is iT,∞ = 4nFDCa where F is Faraday’s constant, n is the number of large: (1). the process at a large substrate is always electrons transferred in the tip reaction (O + ne → R), non-steady state; (2). a large substrate current may D is the diffusion coefficient of species O, C is the cause significant iR-drop; and (3). the collection concentration, and a is the tip radius. When the tip is efficiency, i.e., the ratio of the tip current to the moved toward the surface of an insulating substrate, the substrate current, is low. The tip-generation/substrate- collection (TG/SC) mode is advisable for kinetic tip current, iT, decreases because the insulating sheath of the tip blocks diffusion of O to the tip from the bulk measurements, while SG/TC can be used for solution. The closer the tip gets to the substrate, the monitoring enzymatic reactions, corrosion, and other heterogeneous processes at the substrate surface. smaller iT becomes (Fig 1B). On the other hand, with a conductive substrate, species R can be oxidized back to II. Applications O. This produces an additional flux of O to the tip and hence an increase in iT (Fig. 1C). In this case, the A. Imaging and positioning smaller the value of d, the larger iT will be, with iT → ∞ A three-dimensional SECM image is obtained by as d → 0, assuming the oxidation of R on the substrate scanning the tip in the x-y plane and monitoring the tip is diffusion-limited. These simple principles form the basis for the feedback mode of SECM operation.

Figure 1. Operating principles of SECM. (A). With UME far from the substrate, diffusion of O leads to a steady-state current, iT,∞; (B). With the UME placed near an insulating substrate, hindered diffusion of O Figure 2. SECM image of a polycarbonate filtration membrane with a 2-µm-diameter Pt disk UME in leads to iT < iT,∞; (C). with UME near a conductive 4- Fe(CN)6 solution. Average pore diameter is ca. 10 substrate, positive feedback of O leads to iT > iT,∞. µm.

20 current, iT, as a function of tip location. A particular Of the oxidation of ferrocene at a Pt UME has been advantage of SECM in imaging applications, compared carried out.4e Five steady-state voltammograms to other types of scanning probe microscopy, is that the obtained at different distances are shown in Fig. 3, response observed can be interpreted based on fairly along with the theoretical curves calculated with the rigorous theory, and hence the measured current can be values of the kinetic parameters extracted from the employed to estimate the tip-substrate distance. quartile potentials. The heterogeneous rate constant, ko, Moreover, SECM can be used to image the surfaces of obtained (3.7 ± 0.6 cm/sec) remains constant within the different types of substrates, both conductors and range of experimental error, while the mass-transfer insulators, immersed in solutions. The resolution rate increases with a decrease in d. attainable with SECM depends upon the tip radius. For C. Studies of homogeneous chemical reactions example, Fig. 2 shows one SECM image of a filtration As mentioned above, the TG/SC (with small tip and membrane obtained with a 2-µm-diameter Pt disk tip in substrate) mode of SECM, in the same manner as the 4- Fe(CN)6 solution. Average pore diameter is ca. 10 rotating ring disk electrode (RRDE), is particularly µm. An image demonstrating the local activity of an suitable for the studies of homogeneous chemical enzymatic reaction on a filtration membrane is shown kinetics.1b,5 The SECM approach has the advantage that in Fig. 9 as described below. different substrates can be examined easily, i.e., B. Studies of heterogeneous electron transfer without the need to construct rather difficult to reactions fabricate RRDEs, and higher interelectrode fluxes are SECM has been employed in heterogeneous kinetic available without the need to rotate the electrode or studies on various metal, carbon and semiconductor otherwise cause convection in the solution. Moreover, substrates.4 In this application, the x-y scanning feature in the TG/SC mode, the collection efficiency in the of SECM is usually not used. In this mode, SECM has absence of perturbing homogeneous chemical reaction many features of UME and thin layer electrochemistry is near 100%, compared to significantly lower values in with a number of advantages. For example, the practical RRDEs. Finally, although transient SECM characteristic flux to an UME spaced a distance, d, measurements are possible, most applications have from a conductive substrate is of the order of DC/d, involved steady-state currents, which are easier to independent of the tip radius, a, when d < a. Thus, very measure and are not perturbed by factors like double- high fluxes and thus high currents can be obtained. For layer charging and also allow for signal averaging. example, the measurement of the very fast kinetics For example, the reductive coupling of both dimethyl- fumarate (DF) and fumaronitrile (FN) in N,N-dimethyl formamide has been studied with the TG/SC mode.5a Fig. 4 shows tip and substrate steady-state voltammograms for the TG/SC regime. Comparable values of both of the plateau currents indicated that the mass

Figure 3. Tip steady-state voltammograms for the oxidation of 5.8 mM ferrocene in 0.52 M TBABF4 in MeCN at a 1.1-µm-radius Pt tip. Solid lines are theoretical curves and solid circles are experimental Figure 4. SECM voltammograms for FN (28.2 mM) data. Tip-substrate separation decreases from 1 to 5 reduction in TG/SC mode. d = 1.8 µm. ET was (d/a = ∞, 0.27, 0.17, 0.14, and 0.1). (Reprinted with scanned at 100 mV/sec with ES = 0.0 V vs AgQRE. permission from Ref. 4e, copyright 1993, American (Reprinted with permission from Ref. 5a, copyright Chemical Society.) 1992, American Chemical Society.)

Figure 6. T/S CVs (A) curve a, d = 500 µm, and substrate CV (B) on Nafion/Os(bpy) 3+/2+ electrode in Figure 5. Normalized tip (generation, A) and substrate 3 K3Fe(CN)6/Na2SO4, scan rate = 50 mV/sec, ET = -0.4 (collection, B) current-distance behavior for FN V vs. SCE. (Reprinted with permission from Ref. 6a, reduction. FN concentration: (open circle) 1.50 mM, copyright 1990, American Chemical Society.) (open square) 4.12 mM, (open triangle) 28.2 mM, and (filled circle) 121 mM. a = 5 µm, substrate radius is 50 2+ electrochemical behavior of an Os(bpy)3 -incorporated µm. The solid lines represent the best theoretical fit for Nafion film.6a T/S CV involves monitoring the tip each set of data. (Reprinted with permission from Ref. current vs. the substrate potential (ES) while the tip 5a, copyright 1992, American Chemical Society.) potential (ET) is maintained at a given value and the tip is held near the substrate. The substrate CV (iS vs. ES) 2+ of an Os(bpy)3 -incorporated Nafion film covering a transfer rate was sufficiently fast to study the rapid 3- Pt disk electrode in Fe(CN)6 solution only shows a homogeneous reaction. From the approach curves of 2+/3+ wave for the Os(bpy)3 couple (Fig. 6B), indicating both tip and substrate currents (Fig. 5) obtained at the permselectivity of the Nafion coating. Fig. 6A various FN concentrations, a rate constant kc = 2.0 (± shows the corresponding T/S CV curves. When the tip 0.4) x 105 M-1s-1 was determined for the dimerization is far from the substrate, iT is essentially independent of reactions. ES. When the tip is close to the substrate (d = 10 µm), D. Characterization of thin films and membranes either negative or positive feedback effects are SECM is also a useful technique for studying thin observed, depending on the oxidation state of the films on interfaces. Both mediated and direct 2+/3+ Os(bpy)3 couple in the Nafion. When ES is swept electrochemical measurements in thin films or 2+/3+ positive of the Os(bpy)3 redox wave, a positive membranes can be carried out. For example, feedback effect is observed due to the regeneration of polyelectrolytes, electronically conductive polymers, 3- Fe(CN)6 in the solution gap region because of the passivation films on metals and dissolution processes oxidation of Fe(CN) 4- by Os(bpy) 3+ at the solution- have been investigated by SECM.6 A unique type of 6 3 film interface. When ES is negative of the redox wave, cyclic voltammetry, called tip-substrate cyclic the film shows negative feedback behavior, since the voltammetry (T/S CV), has been used to investigate the

2+ Os(bpy)3 formed is unable to oxidize tip-generated 4- 3- Fe(CN)6 back to Fe(CN)6 . E. Liquid-liquid interfaces One of the most promising applications of SECM is the study of charge transport at the interface between two immiscible electrolyte solution (ITIES).7 Unlike conventional techniques, SECM allows for the studies of both ion and electron transfer at the interface. For example, uphill electron transfer, in which an electron is transferred uphill from a redox couple with a higher standard reduction potential in one phase to another redox couple having a lower standard reduction potential in a second immiscible phase has been demonstrated using the system TCNQ (in 1,2- 7c dichroloethane (DCE))/ferrocyanide (in water). Fig. 7 Figure 8. Approach curve for the system: 10 mM shows the approach curve obtained as the UME TCNQ and 1 mM TPAsTPB in DCE // 1 mM 3- approaches the interface when the system contains Fe(CN)6 , 0.1 M LiCl and 1 mM TPAsCl in H2O, supporting electrolytes with no partitioning ions such showing reverse electron transfer driven by phase + as tetraphenylarsonium (TPAs ). However, the reverse transfer catalyst TPAs+. Tip potential, -0.4 V vs electron flow for the same redox reaction can be Ag/AgCl. (Reprinted with permission from Ref. 7c, + induced by employing TPAs as a potential- copyright 1995, American Chemical Society.) determining ion as shown in Fig. 8. The driving force for this reverse electron transfer is the imposition of an Since the ITIES is not polarizable in the presence of interfacial potential difference by the presence in TPAs+ in both phases, any attempt to impose externally + w solution of TPAs in both phases (∆o ϕ = -364 mV). a potential across the interface with electrodes in two Note that the detection of reverse electron flow in this phases would result in interfacial ion transfer and a case could not be done using the method commonly current flow. The SECM approach does not suffer used for studies of the ITIES, e.g., cyclic form this interference. Charge transfer processes voltammetry. across the ITIES with or without membranes have also been studied. F. Probing patterned biological systems SECM has been actively employed to probe artificially or naturally patterned biological systems.8 Both amperometric and potentiometric techniques with ion-selective tips can be used. A direct test of the SECM’s ability to image an enzymatic reaction over a localized surface region8a is shown in Fig. 9. Glucose oxidase (GO) hydrogel was filled inside small, well- defined pores of polycarbonate filtration membranes. The buffered assay solution contained a high concentration of D-glucose as well as two redox mediators, methyl viologen dication (MV2+) and neutral hydroquinone (H2Q). Fig. 9a shows an image obtained with a tip potential of -0.95 V vs. a silver quasi reference electrode (AgQRE) where MV2+ was reduced to MV+.. Since MV+. does not react with

reduced GO at the hydrogel-filled region, a negative Figure 7. Approach curve for the system: 10 mM feedback current was obtained. However, with the tip 3- potential changed to 0.82 V, where hydroquinone was TCNQ and 1 mM TPAsTPB in DCE // 1 mM Fe(CN)6 oxidized to p-benzoquinone by reduced GO, an and 0.1 M LiCl in H2O, showing the absence of electron transfer across the liquid/liquid interface. A increased tip current was observed (Fig. 9b). This 25-µm-diameter Pt microelectrode was used to generate positive feedback current over the hydrogel region 4- 3- indicates a significant catalytic feedback of the Fe(CN)6 at the electrode tip from the Fe(CN)6 . Tip potential, -0.4 V vs Ag/AgCl. (Reprinted with hydroquinone and provides a direct image of the local permission from Ref. 7c, copyright 1995, American enzymatic reaction. Chemical Society.)

electrode (in deposition reactions) or as the counterelectrode (in etching processes). The feedback mode of fabrication utilizes the same arrangement as in SECM imaging. The tip reaction is selected to generate a species that reacts at the substrate to promote the desired reaction, i.e., deposition or etching. For example, a strong oxidant, like Br2, generated at the tip can etch the area of the substrate, e.g., GaAs, directly beneath the tip.9d The mediator reactant is chosen to be one that reacts completely and rapidly at the substrate, thus confining the reaction to a small area on the substrate and producing features of area near that of the tip. Small tip size and close tip-substrate spacing are required for high resolution.

III. References 1. (a). A. J. Bard, F.-R. F. Fan, J. Kwak, and O. Lev, Anal. Chem. 1989, 61, 132; (b). A. J. Bard, F.-R. F. Fan, and M. V. Mirkin in Electroanalytical Chemistry, Vol.18 (A. J. Bard, ed.), Marcel Dekker, New York, 1994, p. 243. 2. e.g., (a). For a review of early potentiometric SECM experiments, see Ref. 1b; (b). C. Wei, A. J. Bard, G. Nagy, and K. Toth, Anal. Chem. 1995, 67, 1346; (c). K. Toth, G. Nagy, C. Wei, and A. J. Bard, Electroanal. 1995, 7, 801; (d). M. Kupper and J. W. Schultze, Fres. J. Anal. Chem. 1996, 356, 187. 3. See also (a). R. C. Engstrom, M. Weber, D. J. Wunder, R. Burgess, and S. Winquist, Anal. Chem. 1986, 58, 844; (b). R. C. Engstrom, T. Meaney, R. Tople, and R. M. Wightman, Anal. Chem. 1987, 59, Figure 9. SECM images (50 µm x 50 µm) of a single 2005. GO hydrogel-filled pore on the surface of a treated 4. e.g., (a). D. O. Wipf and A. J. Bard, J. Electrochem. membrane. Images were taken with a carbon Soc. 1991, 138, 469; (b). B. R. Horrocks, M. V. microelectrode tip (a = 4.0 µm). (a). Negative Mirkin, and A. J. Bard, J. Phys. Chem. 1994, 98, 2+ feedback with MV mediator at tip potential -0.95 V 9106; (c). R. S. Hutton and D. E. Williams, vs AgQRE. (b). Positive feedback with hydroquinone Electrochim. Acta, 1994, 39, 701; (d). N. Casillas, mediator at tip potential +0.82 V vs AgQRE in 0.1 M P. James, and W. H. Smyrl, J. Electrochem. Soc. phosphate-perchlorate buffer (pH 7.0) containing 100 1995, 142, L16; (e). M. V. Mirkin, T. C. Richards, mM D-glucose, 50 µM hydroquinone and 0.1 mM and A. J. Bard, J. Phys. Chem. 1993, 97, 7672; (f). MVCl2. Lightest image regions depict the greatest tip M. V. Mirkin, L.O.S. Bulhoes, and A. J. Bard, J. current. (Reprinted with permission from Ref. 8a, Am. Chem. Soc. 1993, 115, 201; (g). J. V. copyright 1993, American Chemical Society.) Macpherson, M. A. Beeston, and P. R. Unwin, J. Chem. Soc. Faraday Trans. 1995, 91, 899. 5. e.g., (a). F. M. Zhou, P. R. Unwin, and A. J. Bard, J. Phys. Chem. 1992, 96, 4917; (b). P.R. Unwin and G. Fabrication A. J. Bard, J. Phys. Chem. 1991, 95,7814; (c). F. M. The SECM can be used to fabricate microstructures Zhou and A. J. Bard, J. Am Chem. Soc. 1994, 116, on surfaces by deposition of metal or other solids or by 393; (d). D. A. Treichel, M. V. Mirkin, and A. J. etching of the substrate.9 Two different approaches Bard, J. Phys. Chem. 1994, 98, 5751; (e). C. have been used, the direct mode9a,b and the feedback Demaille, P. R. Unwin, and A. J. Bard, J. Phys. mode9c. Typically, in the direct mode, the tip, held in Chem. 1996, 100, 14137. close proximity to the substrate, acts as a working

100, 17881; (f). C. J. Slevin, J. A. Umbers, J. H. 6. e.g., (a). C. Lee and A. J. Bard, Anal. Chem. 1990, Atherton, and P. R. Unwin, J. Chem. Soc. Faraday 62, 1906; (b). C. Lee, J. Kwak, and F. C. Anson, Trans. 1996, 92, 5177; (g). Y. H. Shao, M. V. Anal. Chem. 1991, 63, 1501; (c). J. Kwak, C. Lee, Mirkin, and J. F. Rusling, J. Phys. Chem. B 1997, and A. J. Bard, J. Electrochem. Soc. 1990, 137, 101, 3202; (h). M. Tsionsky, A. J. Bard, and M. V. 1481; (d). C. Lee and F. C. Anson, Anal. Chem. Mirkin, J. Am. Chem. Soc. 1997, 119, 10785; (i). 1992, 64, 250. (e). I. C. Jeon and F. C. Anson, Anal. M.-H. Delville, M. Tsionsky, and A. J. Bard, Chem. 1992, 64, 2021; (f). M. V. Mirkin, F.-R. F. (submitted to J. Am. Chem. Soc. for publication). Fan, and A. J. Bard, Science, 1992, 257, 364. (g). 8. e.g., (a). D. T. Pierce and A. J. Bard, Anal. Chem. M. Arca, M. V. Mirkin, and A. J. Bard, J. Phys. 1993, 65, 3598; (b). B. R. Horrocks, D. Schmidtke, Chem. 1995, 99, 5040; (h). M. Pyo and A. J. Bard, A. Heller, and A. J. Bard, Anal. Chem. 1993, 65, Electrochim. Acta 1997, 42, 3077; (i). E. R. Scott, 3605; (c). H. Yamada, H. Shiku, T. Matsue, and I. A. I. Laplaza, H. S. White, and J. B. Phipps, Uchida, Bioelectrochem. Bioenerg. 1994, 33, 91; Pharmaceut. Res. 1993, 10, 1699; (j). S. R. Snyder (d). B. Grundig, G. Wittstock, U. Rudel, and B. and H. S. White, J. Electroanal. Chem. 1995, 394, Strehlitz, J. Electroanal. Chem. 1995, 395, 143; (e). 177; (k). S. B. Basame and H. S. White, J. Phys. G. Wittstock, K. J. Yu, H. B. Halsall, T. H. Chem. 1995, 99,16430; (l). N. Casillas, S. Ridgway, and W. R. Heineman, Anal. Chem. 1995, Charlebois, W. H. Smyrl, and H. S. White, J. 67, 3578; (f). H. Shiku, T. Matsue, and I. Uchida, Electrochem. Soc. 1994, 141, 636; (m). D. O. Wipf, Anal. Chem. 1996, 68, 1276; (g). J. L. Gilbert, S. M. Colloid Surf. A, 1994, 93, 251. (n). E. R. Scott, H. S. Smith, and E. P. Lautenschlager, J. Biomed. Mater. White, and J. B. Phipps, Solid State Ionics 1992, 53, Res. 1993, 27, 1357; (h). C. Kranz, T. Lotzbeyer, H. 176; (o). S. Nugnes and G. Denuault, J. Electroanal. L. Schmidt, and W. Schuhmann, Biosens. Chem. 1996, 408, 125; (p). M. H. T. Frank and G. Bioelectron. 1997, 12, 257; (i). C. Kranz, G. Denuault, J. Electroanal. Chem. 1993, 354, 331; Wittstock, H. Wohlschlager, and W. Schuhmann, (q). J. V. Macpherson and P. R. Unwin, J. Chem. Electrochim. Acta, 1997, 42, 3105; (j). C. Lee, J. Soc. Faraday Trans. 1993, 89, 1883; (r). J. V. Kwak, and A. J. Bard, Proc. Natl. Acad. Sci. U.S.A. Macpherson and P. R. Unwin, J. Phys. Chem. 1994, 1990, 87, 1740; (k). R. B. Jackson, M. Tsionsky, Z. 98, 1704; (s). J. V. Macpherson and P. R. Unwin. J G. Cardon, and A. J. Bard, Plant Physiol. 1996, Phys. Chem. 1995, 99, 14824; 1996, 100, 19475; (t). 112, 354; (l). M. Tsionsky, Z. G. Cardon, A. J. J. V. Macpherson, C. J. Slevin, and P. R. Unwin, J. Bard, and R. B. Jackson, Plant Physiol. 1997, 113, Chem. Soc. Faraday Trans. 1996, 92, 3799; (u). K. 895. Borgwarth, C. Ricken, D. G. Ebling, and Heinze, 9. e.g., (a). C. W. Lin, F.-R. F. Fan, and A. J. Bard, J. Ber. Bunsenges. Phys. Chem. 1995, 99, 1421; (v). Electrochem. Soc. 1987, 134, 1038; (b). D. H. Y. Y. Zhu and D. E. Williams, J. Electrochem. Soc. Craston, C. W. Lin, and A. J. Bard, J. Electrochem. 1997, 144, L43; (w). C. Jehoulet, Y. S. Obeng, Y. T. Soc. 1988, 135, 785; (c). D. Mandler and A. J. Bard, Kim, F. M. Zhou, and A. J. Bard, J. Am. Chem. Soc. J. Electrochem. Soc. 1989, 136, 3143; (d). D. 1992, 114, 4237; (x). E. R. Scott, H. S. White, and Mandler and A. J. Bard, J. Electrochem. Soc. 1990, J. B. Phipps, J. Membrane Sci.. 1991, 58, 71; (y). H. 137, 2468; (e). O. E. Husser, D. H. Craston, and A. Sugimura, T. Uchida, N. Kitamura, and H. J. Bard. J. Vac. Sci. Technol. B 1988, 6, 1873; (f). Masuhara, J. Phys. Chem. 1994, 98, 4352; (z). J. E. Y.-M. Wuu, F.-R. F. Fan, and A. J. Bard, J. Vitt and R. C. Engstrom, Anal. Chem. 1997, 69, Electrochem. Soc. 1989, 136, 885; (g). H. Sugimura, 1070. T. Uchida, N. Shimo, N. Kitamura, and H. 7. e.g., (a). C. Wei, A. J. Bard, and M. V. Mirkin, J. Masuhara, Ultramicroscopy 1992, 42, 468; (h). I. Phys. Chem. 1995, 99, 16033; (b). T. Solomon and Shohat and D. Mandler, J. Electrochem. Soc. 1994, A. J. Bard, J. Phys. Chem. 1995, 67, 2787; (c). T. 141, 995; (i). S. Meltzer and D. Mandler, J. Chem. Solomon and A. J. Bard, J. Phys. Chem. 1995, 99, Soc. Faraday Trans. 1995, 91, 1019; (j). C. Kranz, 17487; (d). Y. Selzer and D. Mandler, J. H. E. Gaub, and W. Schuhmann, Advan. Mater. Electroanal. Chem. 1996, 409, 15; (e). M. Tsionsky, 1996, 8, 634; (k). J. F. Zhou and D. O. Wipf, J. A. J. Bard, and M. V. Mirkin, J. Phys. Chem. 1996, Electrochem. Soc. 1997, 144, 1202.

25 Model 1000A Series Multi-Potentiostat

The model 1000A series is a computerized 8 channel potentiostat. The system contains a digital function generator, a multiplexed data acquisition circuitry, a multi-potentiostat can work with eight independent cells, or eight working electrodes in the same solution with a common reference electrode and a common counter electrode. The potential control range is ±10 V for the all channels. All channels can be set at independent potential, or the identical potential as the primary channel, so that they can sweep or step potentials together with the primary channel. Each electrode can be individually controlled, including on/off control, potential and sensitivity settings. The current range is ±10 mA. The instrument is capable of measuring current down to picoamperes. The model 1000A series is an upgraded version from the model 1000 series. The new design allows eight independent cells, simultaneous or sequential measurements, much faster data acquisition speed (1M Hz @16-bit), lower in noise, and easier software update using FLASH memory. Besides the commonly used cyclic voltammetry and amperometric i-t measurements, many other electrochemical techniques are available in the 1000A series. All eight channels can be used for various electrochemical techniques, except open circuit potential measurements. The parameters for all the channels should be set before running experiments. You can not alter the parameter setting during experiments. During run, you can alter display mode between single data set display and multi-set data display (either parallel or overlay plots). After a run, you can choose data sets of any channels as parallel plots or overlay plots. The instrument is controlled by an external PC under the Windows 95/98/NT/Me/2000/XP operating systems using USB or serial port. The instruments are easy to install and use. No plug-in card or other hardware is required on the PC side. The commands, parameters, and options are in terminology that most chemists are familiar with. The toolbar allows quick access to the most commonly used commands. The systematic and complete help system provides context-sensitive help. The instrument provides many powerful functions, such as file handling, experimental control, graphics, data analyses, and digital simulation. Some of the unique features include macro command, working electrode conditioning, color, legend and font selection, data interpolation, visual baseline correction, data point removal, visual data point modification, signal averaging, Fourier spectrum, and equations relating to electrochemical techniques. The maximum data length is 128K – 4096K points (selectable) if real-time data transfer is allowed. The software is 32-bit version and has a multi-document interface.

26 Differences of 1000A Series Models

Functions 1000A 1010A 1020A 1030A Cyclic Voltammetry (CV) z z z z Linear Sweep Voltammetry (LSV) & z z z z Chronoamperometry (CA) z Chronocoulometry (CC) z Differential Pulse Voltammetry (DPV) & z z Normal Pulse Voltammetry (NPV) & z z Square Wave Voltammetry (SWV) & z z Amperometric i-t Curve (i-t) z z z Differential Pulse Amperometry (DPA) z z Triple Pulse Amperometry (TPA) z z Sweep-Step Functions (SSF) z Multi-Potential Steps (STEP) z Open Circuit Potential - Time (OCPT) z z z z

Full version of CV simulator z Limited version of CV simulator z z z

&: Corresponding stripping mode can be performed.

Specifications

8-Channel potentiostat CV and LSV scan rate: 0.000001 to 5000 V/s (8 independent cells or a multi-working electrode cell) CA and CC pulse width: 0.0001 to 1000 s Potential range (all channels): ±10 V CA and CC Steps: 320 Compliance voltage: ±12 V DPV and NPV pulse width: 0.001 to 10 s Current range (each channel): 10 mA SWV frequency: 1 to 100K Hz Reference electrode input impedance: 1×1012 ohm Current low-pass filters Sensitivity scale: 1×10-9 - 0.001 A/V in 7 ranges Current analog output Input bias current: < 50 pA Cell control: purge, stir, knock Current measurement resolution: < 1 pA Maximum data length: 128000 points each channel Data acquisition: 16 bit @ 1M Hz maximum Chassis dimension: 12.5”(W) × 11”(D) × 4.75”(H)

Overlay plot of 8 channel i-t Curve with different Overlay plot of 8 channel SWV with all eight channel potential setting for each channel potential scanned simultanousely

27 Model 1100A Series Power Potentiostat / Galvanostat

The Model 1100A series power potentiostat/galvanostat is designed for electrochemical applications that require relatively large current and high compliance voltage, such as battery, corrosion, electrolysis, and electroplating. The current range is ± 2 A. The compliance voltage is ± 26 V. The instrument contains a digital function generator, a data acquisition system, filters for the current signals, iR compensation circuitry, a potentiostat, and a galvanostat (Model 1140A). The potential control range is ± 10 V. The 1100 series is capable of measuring current down to tens of picoamperes. The steady state current of a 10 µm disk electrode can be readily measured without external adapters. The instrument is reasonably fast. For instance, the scan rate in cyclic voltammetry can be up to 1000 V/s. Multiple data acquisition systems allow an external input signal (such as spectroscopy signals to be recorded simultaneously with electrochemical data). The model 1100A series is the upgrade from the model 1100 series. The redesigned instrument contains a new processor (about 50 times faster than the 1100) and FLASH memory (allowing instrument updates to be distributed by e-mail instead of the shipment of an EPROM chip). The maximum sampling rate is 200 KHz. The 1100A series has a serial port (default) and a USB for data communication with the PC. You can select either serial port or USB (but not both) by changing the jumper setting on the board. A 16-bit highly stable bias circuitry is added for current or potential bias. This allows wider dynamic range is ac measurements. It can also be used to re-zero the dc current output. There are some other improvements. New techniques, such as AV Voltammetry (ACV), Second Harmonic AC Voltammetry (SHACV), Multi-Current Steps (ISTEP) have been added to the model 1100A series. ISTEP allows cycling through 12 current steps. Multi-Potential Steps (STEP) also allows cycling through 12 potential steps (cf. 6 steps in model 1100 series).

Chronopotentiometric measurement

28 Specifications

Potentiostat CV and LSV scan rate: 0.000001 to 2000 V/s Galvanostat (Model 1140A) Minimum potential increment during scan: 0.1 mV Potential range: -10 to 10 V CA and CC pulse width: 0.001 to 1000 s Potentiostat rise time: < 2 µs CA and CC Steps: 320 Compliance voltage: ± 26 V DPV and NPV pulse width: 0.001 to 10 s 3- or 4-electrode configuration SWV frequency: 1 to 10 kHz Current range: ± 2 A Automatic potential and current zeroing Reference electrode input impedance: 1×1012 ohm Signal low-pass filters, covering 8-decade frequency Sensitivity scale: 1×10-12 - 0.1 A/V in 34 ranges range, Automatic and manual setting Input bias current: < 100 pA Potential and current analog output Current measurement resolution: < 1 pA Cell control: purge, stir, knock Potential update rate: 1 MHz Automatic potential and current zeroing Data acquisition: 16 bit @ 200 kHz Current low-pass filters, covering 8-decade frequency External voltage signal recording channel range, Automatic and manual setting External potential input Flash memory for quick software update Automatic and manual iR compensation Serial port or USB selectable for data communication Potential and current analog output Maximum data length: 128K-4096K selectable RDE control voltage output: 0-10V (1130 and up) Chassis dimension: 12.5”(W) × 11”(D) × 4.75”(H) Weight: 18 Lb.

Differences of 1100A Series Models

Fu nctions 1100A 1110A 1120A 1130A 1140A Cyclic Voltammetry (CV) z z z z z Linear Sweep Voltammetry (LSV) & z z z z z Staircase Voltammetry (SCV) #,& z z Tafel Plot (TAFEL) z z Chronoamperometry (CA) z z z z Chronocoulometry (CC) z z z z Differential Pulse Voltammetry (DPV) #,& z z z z Normal Pulse Voltammetry (NPV) #,& z z z z Differential Normal Pulse Voltammetry (DPNV)#,& z Square Wave Voltammetry (SWV) & z z z AC Voltammetry (ACV) #,&,$ z z 2nd Harmonic AC Voltammetry (SHACV) #,&,$ z z Amperometric i-t Curve (i-t) z z Differential Pulse Amperometry (DPA) z Double Differential Pulse Amperometry (DDPA) z Triple Pulse Amperometry (TPA) z Bulk Electrolysis with Coulometry (BE) z z z z Sweep-Step Functions (SSF) z Multi-Potential Steps (STEP) z Chronopotentiometry (CP) z Chronopotentiometry with Current Ramp (CPCR) z Multi-Current Steps (ISTEP) z Potentiometric Stripping Analysis (PSA) z Open Circuit Potential - Time (OCPT) z z z z z

Galvanostat z RDE control (0-10V output) Full version of CV simulator z z Limited version of CV simulator z z z iR Compensation z z z z z External Potential Input z z z z z Auxiliary Signal Measurement Channel z z z z z

#: Corresponding polarographic mode can be performed. &: Corresponding stripping mode can be performed.

29 Model 1200A Series Hand-held Potentiostat / Bipotentiostat

The Model 1200A series is a computerized hand-held potentiostat/bipotentiostat. The instrument consists of a digital function generator, a data acquisition system, and a potentiostat/bipotentiostat. The potential range is ± 2.4 V. The current range is ± 2 mA. This series is capable of measuring current down to 100 pA. The steady state current of a 10 µm disk electrode can be readily measured. The size of the instrument is 7” (L) × 4.5” (W) × 1” (H). The instrument is powered by the USB port of a PC computer, without need of an external wall transformer or batteries. It is therefore more compact and convenient. The instrument can be used for electroanalysis and sensor studies. Due to its small size, light weight, and low cost, it is particularly useful for field applications and teaching laboratories. Compared with the previous Model 1200 series, the new design allow ±7.5 V compliance voltage, which ensures the working potential range ±2.4 V for most of the electrochemical systems. It also uses dual 16-bit DAC and 16-bit ADC for improved resolution and accuracy. The instrument provides many powerful functions, such as file handling, experimental control, graphics, data analysis, and digital simulation. Some of the unique features include macro command, working electrode conditioning, color, legend and font selection, data interpolation, visual baseline correction, data point removal, visual data point modification, signal averaging, Fourier spectrum, and equations relating to electrochemical techniques. The CHI1200A series provides various instrument models to meet different applications and budget., and is available in potentiostat (CHI1200A, 1210A, 1220A, and 1230A) and bipotentiostat versions (CHI1202A, 1212A, 1222A, and 1232A).

Specifications

Potentiostat / bipotentiostat CV and LSV scan rate: 0.000001 to 10 V/s Maximum potential range: ± 2.4 V CA and CC pulse width: 0.001 to 1000 s Compliance voltage: ± 7.5 V CA and CC Steps: 1 - 320 Current range: ± 2 mA DPV and NPV pulse width: 0.001 to 10 s Reference electrode input impedance: 1×1012 ohm SWV frequency: 1 to 5000 Hz Sensitivity scale: 1×10-10 - 0.001 A/V in 8 ranges Low pass filter for current measurements Input bias current: < 100 pA Maximum data length: 128K-4096K selectable Current measurement resolution: < 5 pA Power: UPS port of a PC Data acquisition: 16 bit @ 10 kHz Chassis dimension: 7” (W) × 4.5” (D) × 1” (H)

Differences of 1200A Series Models

Functions 1200A 1205A 1207A 1210A 1220A 1230A /1202A /1206A /1208A /1212A /1222A /1232A Cyclic Voltammetry (CV)* z z z z z z Linear Sweep Voltammetry (LSV) &,* z z z z z z Chronoamperometry (CA)* z z z Chronocoulometry (CC) z z z Differential Pulse Voltammetry (DPV) &,* z z z Normal Pulse Voltammetry (NPV) &,* z z z Differential Normal Pulse Voltammetry (DPNV) &,* z Square Wave Voltammetry (SWV) &,* z z Amperometric i-t Curve (i-t)* z z z Differential Pulse Amperometry (DPA) z z Double Differential Pulse Amperometry (DDPA) z z Triple Pulse Amperometry (TPA) z z Open Circuit Potential - Time (OCPT) z z z z z z

Full version of CV simulator z Limited version of CV simulator z z z z z

&: Corresponding stripping mode can be performed. *: Second channel (bipotentiostat mode) can be performed.

30 CHI1550A Solution Dispenser

The CHI1550A solution dispenser is designed for making high density and high accuracy solution arrays. Solution arrays are widely used in chemical, biological and medical applications. The solution dispenser consists of a high resolution three dimensional positioner, a piezoelectric jetting device, and a sample platform. The diagram is shown in Figure 1.1.

Figure 1. Diagram of the solution dispenser

The three dimensional positioner can travel 50 mm distance for all three axes with 0.1 micrometer resolution. This allows high precision patterning. This is particularly important when multiple solution components need to be dispensed overlapped. The jetting device can dispense single drop of fluids. Typical fluids successfully jetted in this device have viscosity less than 40 centipoise and surface tension in the range of 0.02-0.07 N/m. Fluids with properties outside these limits can be jetted if changes to the properties can be achieved with solvents or changes in temperature. With a default 60 micron orifice size, the jetting device can produce drops ranging from 100-200 picoliters in volume depending on the operating parameters and fluids. The CHI1550A solution dispenser control software is very user-friendly for creating binary, ternary and quadruple arrays of spots containing mixtures of solutions. Instead of using a manually created look-up table for solution dispensing patterns, the software will assist the pattern creation. The software can also provide commonly used patterns as default for binary, ternary and quadruple arrays. The positioner can memorize certain critical positions, such as solution loading point and first dispense point. This will help the jetting device to go to these positions easily and quickly. The array pattern can be examined graphically. During dispensing process, the array pattern will also be displays as the dispensing progresses.

31 Figure 3. Micropositioner and sample stand

System requirements

Operating System: PC with Microsoft Windows 95 / 98 / NT /Me/ 2000 / XP Communication: RS-232 serial port or USB

Hardware Specifications

Micropositioner: Jetting Device:

Three high resolution stepper motors Orifice side of the jetting device: 60 micron • Maximum range of motion: 25 mm Droplet size: 100-200 picoliters Control voltage: 0-150V • Motor resolution: 100 nm A protective holder for the jetting device • Stall Load: 50 N

• Maximum Speed: 4 mm / sec

Three Translation Stages • Maximum range of motion: 25 mm • Angular deviation: < 200 microrad • Load capacity: 156 N • Load capacity (vertical): 67 N

32 CHI200(B) Picoamp Booster and Faraday Cage

With the CHI200(B) Picoamp Booster and Faraday Cage, current down to a few picoamperes can be readily measured. The CHI200 is compatible with the Model 600/A, 700/A series of instruments, while the CHI200B is compatible with Model 600B/C and 700B/C series. When used with 700/A/B/C series bipotentiostat, the Picoamp Booster will affect the primary channel only. The internal sensitivity of the 600C series is the same as the Picoamp Booster (1×10-12 A/V). However, the bias current of the 600B/C series input can be as high as 50 pA. The Picoamp Booster has lower bias current, and it also brings the preamplifier close to the electrode hence resulting in lower noise. The Faraday Cage also makes it possible to make relatively fast measurements of small currents. When the Picoamp Booster is connected and the sensitivity scale is at or below 1×10-8 A/V, the Picoamp Booster will be enabled. Otherwise, it will be disabled. The instruments automatically sense whether a Picoamp Booster is connected. The enable/disable switching is also automatic. The Picoamp Booster will be disabled for techniques using automatic sensitivity switching, such as Tafel plots, bulk electrolysis (BE), and ac impedance (IMP). It is not necessary to disconnect the Picoamp Booster to run those techniques. However, for galvanostatic techniques, such as chronopotentiometry (CP) and potentiometric stripping analysis (PSA), the Picoamp Booster must be disconnected. Besides weak signal measurements, the Faraday cage is useful for eliminating electrical interference, especially line frequency noise. If the electrochemical cell is picking up electrical noise from the environment, the additional use of Faraday cage is strongly recommended.

Dimension: 9.6”(W) × 8.8”(D) × 11.8”(H) Weight: 13 Lb.

Cyclic voltammogram at an ultramicroelectrode. Differential pulse voltammogram at an ultramicroelectrode.

33 Model 680 Amp Booster

With the CHI680 Amp Booster, the current can be measured up to 2 A. The CHI680 is compatible with Model 600, 600A, 600B, and 600C series of instruments. You can stack the CHI600/A/B/C and the CHI680 together. With the Amp Booster connected, the cell control signals such as purge, knock and stir are disabled. The Amp Booster will also allow low current measurements. The current down to 10 pA can be measured. It is comparable with the CHI600/A/B/C alone. You may need to use the Faraday Cage to eliminate line frequency noise when the scan rate is above 50 mV/s. The frequency response of the Amp Booster is somewhat lower than that of the CHI600/A/B/C instruments. For high speed experiments, the Amp Booster should be disconnected.

Dimension: 12.5”(W) × 11”(D) × 4.75”(H) Weight: 18 Lb.

CHI682 Liquid/Liquid Interface Adapter

Liquid/liquid interface study is very important in understanding the charge transfer, chemical sensor, drug release, solvent extraction, and others. Liquid/liquid interface study usually involves two reference electrodes and two auxiliary electrodes. The modified potentiostat controls the potential difference of the two reference electrodes in two phases, while measuring the current passing through two auxiliary electrodes. The CHI682 Liquid/Liquid Interface Adapter is compatible with our model 700A series. It is fully automatic and integrates seamlessly. Although it does not have galvanostat and bipotentiostat functions, most other electrochemical techniques can be used. Please notice that for model 400, 600A, 600B, 600C, 700B, 700C, 800B, 900B, 1100 and 1100A series, a 4-electrode configuration will allow liquid/liquid interface measurement to be made directly without using CHI682 Liquid/Liquid Interface Adapter.

CHI684 Multiplexer

CHI684 is a multi-channel multiplexer for the model 400/A, 600A/B/C, 700A/B/C, 800B, 900B and 1100A series. The multiplexer switches four lines (working, sensing, reference, and counter for a single potentiostat, second working, reference and counter for a bipotentiostat). You can have maximum 64 cells, but only one cell can be connected at a time. The multiplexer is controlled from the "Multiplexer" command under the Control menu. You can select any channel and run experiments in a sequence of the selected channels. The files will automatically be saved after each run. You can also set a prompt before each channel run. It is allowed to set arbitrary channels immediately. An experiment can then be run for that particular channel. Two Macro commands are available for the multiplexer. One is "mch:##". It allows the user to choose an individual channel. The other macro command is "mchn". This is used in a For...Next loop to select the channel according to the For...Next loop counter. The minimum number of channels for the CHI684 are 8. The channel increment is 8. The maximum number of channels are 64.

Highlights

User Interface Instrument Control • 32-bit Windows application • run experiment: real time data • rotating disk electrode: rotation • Multi-Document Interface display in most cases speed, on/off control during • toolbar: quick access to • pause/resume during run deposition, quiescent time, run, frequently used commands • stop running experiment and between runs • status bar: technique and • reverse scan direction during • stripping mode: enable/disable, command prompt run: for cyclic voltammetry deposition potential and time, stir • pull-down menus • repetitive runs: automatic data and purge conditions • WYSIWYG graphics save, signal averaging, delay or • comprehensive and context prompt between runs, up to 999 sensitive help runs Graphic Display • present data plot • run status: stir, purge, iR 3D surface plot: front, rear, side, compensation, smooth after run, • File Management top and bottom view RDE and SMDE control status • reopen saved data files • overlay plots: several sets of • save data file • macro commands: edit, save, data overlaid for comparison • delete files read, and execute a series of • add data to overlay: adding data • list data file commands files to overlay plot • convert to text files: for • open circuit potential • parallel plots: several sets of exporting data to other measurement data plotted side by side software, such as spreadsheets • iR compensation: automatic and • add data to parallel: adding • text file format manual compensation, solution data files to parallel plot • print present data resistance, double layer • zoom in/out: visually selected • print multiple data files capacitance and stability test zoom area • manual results: visually • print setup • analog filter setting: automatic or manual setting of potential, selected baseline i/V converter, and signal filters • peak definition: shape, width,

Setup • cell control: purge, stir, cell on, and report options • technique: a large repertoire SMDE drop collection, and pre- • Special Plots: x-y, i -v, i -v1/2, of electrochemical techniques p p run drop knock Ep-log v, semilog plots, linear • experimental parameters: • step functions: initial and two polarization resistance plot extremely wide dynamic range step potentials, duration of steps • graph options: video or printer • system setup: choice of and number of steps, particularly options, axis, parameters, communication port, line useful for electrode treatment baseline, results, grids, axis frequency, choice polarity of • working electrode conditioning inversion, axis freeze, axis titles, potential and current axis before running experiment: data sets, XY scales, current • hardware test: digital and programmable 3 steps density option, reference analog circuitry diagnostic test electrode, header, and notes

1/2 Overlay plots. Automatic ip ~ v plot. Automatic semilog plot.

Highlights

• color and legend: background, • standard addition: calculation Impedance Simulator axis, grid, curves, legend size, and plot and Fitting Program thickness, and display intervals • data file report: analytical • visual entry of equivalent • font: font, style, size and color report from existing data files circuitry for axis labels, axis titles, header, • time dependence report • automatic equivalent circuit parameters, and results • corrosion rate calculation parameters fitting • copy to clipboard: for pasting the

data plot to word processors CV Digital Simulator View • fast implicit finite difference Data Processing • data information: date, time, algorithm • smoothing: 5-49 point least filename, data source, • reaction mechanisms: 10 square and Fourier transform instrument model, data • derivatives: 1st - 5th order, 5-49 predefined mechanisms (low processing performed, header point least square end models); or any and notes • integration combination involving electron • data listing: data information • convolution: semi-derivative and transfer, first- and second-order and numerical data array • equations: general equations semi-integral chemical reactions (high end and equations relating to • interpolation: 2× - 64× data models) interpolation various electrochemical • system: diffusive or adsorptive • baseline correction: visually techniques selected baseline, slope and dc • maximum equations: 12 • SECM probe status: probe level compensation • maximum species: 9 position and current display • baseline fitting and subtraction: • simulation parameters: • clock selectable fitting function, standard redox potentials, rate • toolbar polynomial order and potential of electron transfer, transfer • status bar range for best fitting and baseline coefficient, concentration, diffusion coefficient, forward subtraction; particularly useful for Help trace analysis and reverse chemical reaction • context sensitive help • data point removing rate constants, temperature, • help topics • data point modifying: visual data electrode area, and • about the application point modification experimental parameters

• background subtraction: • simultaneous display of difference of two sets of data voltammogram and System requirements • signal averaging concentration profiles • operating system: Microsoft Windows 95 / 98 / NT / Me / • mathematical operations: both X • automatic search and 2000 / XP and Y data array determine over-determined • serial communication port or • Fourier spectrum equilibrium constants USB port • dimensionless current Analysis • equilibrium data • calibration curve: calculation and plot

Concentration-time dependence plot. Fourier spectrum. Nyquist plot of impedance data.

Highlights

System setup allows any convention of current and potential polarity.

A large repertoire of electrochemical techniques.

The Macro command allows a series command to be executed in a sequence..

Experimental parameter dialog box for Cyclic Voltammetry.

User interface for digital simulator.

Experimental parameter dialog box for SECM.

Highlights

Digital Simulator displays both current response and the concentration profiles of different species during the simulation Equations relating to various techniques process. can be viewed on line.

Impedance data plot. Chronocoulometric data.

Multi-cycle chronopotentiometric data. Multi-segment sweep-step functions data..

38 Accessories

Part No. Description Unit Part No. Description Unit CHI101 2 mm dia. Gold Working Electrode 1 CHI125A Polished, Bounded, Mounded 100A 1 CHI101P 2 mm dia. Gold Working Electrode 3/pk Ti + 1000 A Gold Crystal for EQCM CHI102 2 mm dia. Platinum Working Electrode 1 CHI127 EQCM Cell 1 CHI102P 2 mm dia. Platinum Working Electrode 3/pk CHI128 Reference Electrode for EQCM Cell 1 CHI103 2 mm dia. Silver Working Electrode 1 CHI129 Pt Wire Counter Electrode for EQCM 1 CHI104 3 mm dia. Glassy Carbon Working 1 Cell Electrode CHI130 Thin-Layer Flow Cell 1 CHI104P 3 mm dia. Glassy Carbon Working 3/pk CHI131 GC Working Electrode for Flow Cell 1 Electrode CHI132 Au Working Electrode for Flow Cell 1 CHI105 12.5 µm dia. Gold Microelectrode 1 CHI133 Pt Working Electrode for Flow Cell 1 CHI134 Reference Electrode for Flow Cell 1 CHI105P 12.5 m dia. Gold Microelectrode 3/pk µ CHI135 25 um Spacer for Flow Cell 4/pk CHI106 1 25 µm dia. Gold Microelectrode CHI140A Spectroelectrochemical Cell 1 CHI106P 25 µm dia. Gold Microelectrode 3/pk CHI150 Calomel Reference Electrode 1 CHI107 10 µm dia. Platinum Microelectrode 1 CHI151 Mercury/Mercurous Sulfate 1 Reference Electrode CHI107P 3/pk 10 µm dia. Platinum Microelectrode CHI152 Alkaline/Mercurous Oxide Reference 1 CHI108 25 µm dia. Platinum Microelectrode 1 Electrode CHI108P 25 µm dia. Platinum Microelectrode 3/pk CHI172- Electrode leads for a particular 1 Model # instrument model number CHI111 Ag/AgCl Reference Electrode 1 CHI200 Picoamp Booster and Faraday Cage 3 1 CHI111P Ag/AgCl Reference Electrode 3/pk CHI201 Picoamp Booster 1 CHI112 Non-Aqueous Ag/Ag+ Reference 1 1 CHI202 Faraday Cage 1 Electrode 4 + CHI220 Simple Cell Stand 1 CHI112P Non-Aqueous Ag/Ag Reference 3/pk Electrode 1 CHI221 Cell Top (including Pt wire counter 1 electrode, not a replacement part for CHI115 Platinum Wire Counter Electrode 1 the CHI200 cell stand) 5 CHI116 1 10 µm dia. Platinum SECM Tip CHI222 Glass Cell 1 CHI116P 10 µm dia. Platinum SECM Tip 3/pk CHI223 Teflon Cap 5 1 CHI117 25 µm dia. Platinum SECM Tip 1 002047 IDA Gold Electrode 1 002048 IDA Platinum Electrode 1 CHI117P 25 m dia. Platinum SECM Tip 3/pk µ 002049 IDA Carbon Electrode 1 CHI118 1-5 µm dia. Platinum SECM Tip 3/pk 011235 CS-2 Remote Controllable Cell Stand 1 CHI120 Electrode Polishing Kit 2 1 011343 QCM Flow Cell 1 TE100 Printed Electrodes (3-electrodes) 40/pk SE101 3mm dia. Printed carbon electrode 40/pk

Notes: + 1. A Ag solution (typical 10 mM) should be prepared with the supporting electrolyte and AgNO3 (not included). This solution is then filled into the reference electrode compartment using a syringe (not included). The instructions will come with the components. 2. The electrode polishing kit contains 1 bottle of 1.0 micron Alpha alumina powder, 1 bottle of 0.3 micron Alpha alumina powder, 3 bottles of 0.05 micron Gamma alumina powder, 2 glass plates for polishing pads, 5 pieces of 73 mm diameter 1200 grit Carbimet disks (grey in color), 5 pieces of 73 mm diameter Mastertex polishing pads (white in color), and 10 pieces of 73 mm diameter Microcloth polishing pads (brown in color). 3. Picoamp Booster and Faraday Cage allows the current measurement down to 1 pA. It is fully automatic and compatible with Model 6xxC and 7xxC series instruments. However, it only works for the primary channel of the 7xxC series . 4. Made of stainless steel and Teflon (see figure below). Not remote-controllable. Four glass cells are included. 5. Not a replacement part for the CHI220 Cell Stand.

39 Accessories and Instrument Chassis

CHI130 Thin-Layer Flow Cell Front and rear view of the Model 400A, 600B, 700B, 800B, 900B, 1000, and 1100A series instruments

40 41 42

Warranty: One-year warranty on electronic parts and labour. 90-day warranty on mechanical parts.

Demo Software: Free demo software available upon request.

In Europe IJ Cambria Scientific . 11 Gwscwm Road . Burry Port . Carms . SA16 OBS . UK Phone: 01554 835050 . Fax: 01554 835060 . E-mail: [email protected] (Mobile: 07957 287343) IJ Cambria Scientific: www.ijcambria.com

In US CH Instruments, Inc. 3700 Tennison Hill Drive . Austin, TX 78733 . USA Tel: (512) 402-0176 . Fax: (512) 402-0186

ã.January 2009 CH Instruments